I'm on a budget, and I'm trying to figure out what material I could use that's lightweight and could look convincingly like metal. Trying to create a chest piece and maybe some segments for the arms.
I like SIntra because it is cheap, super light and easy to cut, glue, sand plus it takes paint really well. Sintra gives off hazardous fumes when heated (for bending), so you need to be careful and use a respirator -also when sanding. There are great videos on youtube on how to use it.
This link shows some simple chest armor made with sintra for one of my son's costumes...
Another +1 for EVA foam. In addition to Evil Ted's tutorials, Bill Duran over at Punished Props has a bunch of fantastic tutorials on making armor, and even has a couple books on the subject.
Edit: totally missed Bill's tutorials were already mentioned. But seriously, some really good stuff for getting started over there.